128 DOMESTICATED TROUT. 



as you can safely, and make the water colder, if pos- 

 sible. You can never make good eggs of them again, 

 but you may arrest its spreading in some degree, and 

 save the lives of some of the embryos. An ounce 

 of prevention is, however, worth a pound of cure, and 

 in this instance it is worth a thousand pounds of 

 cure. Therefore char every box, aqueduct, and trough, 

 and all the wood-work through which the water flows ; 

 then you will have no fungus. It will not form on 

 charcoal in the dark. 



2. Sediment. This is a danger of no small impor- 

 tance, but it is nothing like fungus in its destructive- 

 ness, for it can be removed, it does not spread, and it 

 is not always fatal. It is, however, a very bad thing, 

 and sometimes very troublesome. It consists of the 

 very fine dust which is held mechanically in all run- 

 ning water. As remarked in a previous chapter, it 

 may not be discernible in the water when examined 

 by the eye, but will show its presence after the water 

 has run a certain length of time over a given place, by 

 being precipitated as a light deposit of dirt or mud 

 over the spot. This fine layer of dirt, if it should 

 settle on the eggs, would suffocate them in time, or if 

 not in sufficient quantity to suffocate them would, by 

 interrupting the processes of absorption and growth of 

 the embryo at certain points, cause a deformity in the 

 fish when hatched. Many of the curved spines, 

 hunched backs, and spiral bodies of fish newly hatched 

 are caused by this partial suffocation of the embryo by 

 the sediment. The remedy for sediment, or rather its 

 prevention, as before observed, is the system of filters. 



